Even if we imagine MMT working perfectly — whatever that means — it represents a stealthy redistributing of wealth. The idea behind it is for the government to acquire and then redistribute goods and services from those in the private sector who would otherwise command that wealth, and do something else with it: in other words, give these goods and services to others.

And no one is going to notice this? The people who are used to enjoying some quantity of goods and services are not going to notice that they now enjoy less, because someone else is enjoying them?

Or, is this somehow supposed to "stimulate" the economy, so that more goods and services are actually produced, because of the extra money?

This is alchemy. Production comes before consumption.